SANAA, Yemen — The United States has raised the tempo in its war against al-Qaida in Yemen, killing nine of the terror group's militants in the second, high-profile airstrike in as many weeks. The dead in the late Friday night strike included the son of Anwar al-Awlaki, the prominent American-Yemeni militant killed in a Sept. 30 strike.

Yemeni officials on Saturday attributed the recent U.S. successes against al-Qaida to better intelligence from an army of Yemeni informers and cooperation with the Saudis, Washington's longtime Arab allies.

The successes come even as Yemen falls deeper into turmoil, with President Ali Abdullah Saleh clinging to power in the face of months of massive protests. Saturday saw the worst bloodshed in weeks in the capital, Sanaa: At least 18 people were killed when Saleh's troops fired on protesters and clashed with rivals. Witnesses estimated up to 300,000 people joined Saturday's demonstrations, the largest in the capital in several months.

"Everyone with interests in Yemen, including al-Qaida and the Americans, is raising the stakes at this time of uncertainty" said analyst Abdul-Bari Taher. "The Americans are wasting no time to try and eliminate the al-Qaida threat before the militants dig in deeper and cannot be easily dislodged."

Also dead in the Friday airstrike in the southeastern province of Shabwa was Egyptian-born Ibrahim al-Banna, identified by the nation's Defense Ministry as the media chief of the Yemeni branch of the al-Qaida.

Al-Qaida in the Arabian Peninsula, as the branch is known, is considered by the U.S. the most dangerous of the terror network's affiliates after it plotted two recent failed attacks on American soil. Its fighters and other Islamic militants have taken advantage of Yemen's chaos to seize control of several cities and towns in a southern province. That has raised American fears they can establish a firmer foothold in the strategically located country close to the vast oil fields of the Gulf and overlooking key shipping routes.

The U.S. airstrikes in Shabwa pointed to Washington's growing use of drones to target al-Qaida militants in Yemen. The missile attacks appear to be part of a determined effort to stamp out the threat from the group.

Yemeni officials familiar with the U.S. military drive against al-Qaida in Yemen said a shift of strategy by the Americans was finally yielding results, with human assets on the ground directly providing actionable intelligence to U.S. commanders rather than relying entirely on Yemen's security agencies the Americans had long considered inefficient or even suspected of leaking word on planned operations.

They said there were as many as 3,000 informers on the U.S. payroll around the country – some without even knowing it.

The Saudis, on the other hand, have traditionally kept an elaborate patronage system and an information network in Yemen, their neighbor to the south. They have for decades paid monthly stipends to key tribal leaders, military commanders and politicians to secure their loyalty. They also paid ordinary Yemenis to provide them with intelligence.

"The Saudis are making their information available to the Americans," said one of the defense officials, all of whom spoke on condition of anonymity because they were not authorized to share the information. "Both them and the Americans are broadening their cooperation without direct Yemeni involvement."

Tribal elders in the area where Friday's strikes took place said the dead included Abdul-Rahman al-Awlaki, the 21-year-old son of Anwar al-Awlaki, a Muslim preacher and savvy Internet operator who became a powerful al-Qaida recruiting tool in the West and who was on a U.S. capture-or-kill list. The elder al-Awlaki and another propagandist, Pakistani-American Samir Khan, were killed in the Sept. 30 strike.

The tribal elders, who spoke Saturday on condition of anonymity because they feared reprisals, said four other members of the al-Awlaki clan and another local militant were also killed in the same drone attack. There was no immediate confirmation of the younger al-Awlaki's death from Yemeni authorities.

Security officials said the strike was one of five carried out overnight by American drones on suspected al-Qaida positions in Shabwa and neighboring Abyan province in Yemen's largely lawless south. They said two more militants were killed and 12 wounded in other strikes in the two provinces.

The first strike late Friday targeted a house in the Azan district of Shabwa, but hit just after al-Qaida militants had a meeting in the building, security officials and tribal elders said.

They said a second strike then targeted two sport utility vehicles in which the seven were traveling, destroying the vehicles and leaving the men's bodies charred. It was not clear whether other participants in the meeting were targeted in separate strikes.

Yemen's al-Qaida offshoot has taken advantage of the political turmoil roiling the country. Saleh, who has ruled the country for more than 30 years, has been struggling to stay in power in the face of eight months of massive street protests demanding his ouster and the defection to the opposition of key aides and military commanders.

In a separate development, the security officials said suspected al-Qaida militants bombed a key underground gas pipeline that extends from the Balhaf area in Shabwa to an export terminal on the Arabian Sea. The late Friday night attack started a massive fire, with columns of flames illuminating the night sky.

The security officials said non-Yemeni employees of Total, the French company running the gas field and pipeline in Balhaf, have been evacuated to Sanaa aboard three helicopters for their safety. They had no more details.

In Sanaa, forces loyal to Saleh opened up on protesters with assault rifles and anti-aircraft guns, medical officials and witnesses said. The casualty figures – 12 dead and up to 300 wounded – were confirmed by Mohammed al-Qubati, director of the field hospital set up at Change square, the name given to a central Sanaa intersection that saw the birth of the eight-month-old, anti-Saleh uprising.

The medical officials requested anonymity because they were not allowed to speak to journalists.

In Sanaa's northern district of Hassaba, fighting between Saleh's forces on one side and anti-regime tribesmen and renegade troops on the other killed two civilians and four supporters of tribal chief Sadeq al-Ahmar, a one-time regime ally who defected to the opposition in March. At least 13 people were wounded in the fighting.

A three-story building housing an independent TV station, Al-Saeedah, in the area took a direct hit, destroying the channel's equipment and studios, according to a statement by the management. The privately owned station went off the air.

Khaled al-Ansi, a prominent leader of the protest movement, blamed the death of the protesters on opposition parties, arguing that their acceptance of a U.S.-backed settlement plan proposed by Yemen's Gulf Arab neighbors gave Saleh license to kill protesters at will. The plan provides for the Yemeni leader to step down and hand over power to his deputy in exchange for immunity.

"The political parties are participants in the killings," said al-Ansi. "The immunity from prosecution is giving Saleh a temptation to kill more of us."